As electronic systems become more complex, more compact, and more widely used and relied on, the integrity and reliability of electrical connections between various electrical parts, such as circuit boards carrying electronic components, increases in importance. Circuit boards with electronic components, such as integrated circuits, printed circuit traces, and/or other devices thereon, therein and/or otherwise associated therewith can be manufactured in a controlled environment for quality assurance and at the manufacturing level they can be carefully tested to confirm acceptable operation within specifications. However, as the number of connections of the electronic components increase per area of the circuit board, it becomes more difficult properly to align connection devices, to maintain connections and to test and to examine the connections and the overall electronic systems as they are assembled and used.
Also, as more electronic devices are used in mechanical systems and are subjected to space constraints of those mechanical systems and to mechanical forces and stresses during expected use of the mechanical systems, the difficulty in maintaining integrity of electrical connections increases. The failure of an electrical connection may result in failure of part or all of the mechanical system.
An exemplary mechanical system in which electronics are used, for example, for guidance, communications, munitions operations (e.g., firing), etc., are missiles. The electronics are provided on a plurality of circuit boards, each of which has one or more electronic components, printed circuits, terminal pads, etc. thereon, and the circuit boards are arranged in a stacked or sandwich relation to fit the form factor dictated by the missile shape, for example, a generally hollow cylindrical shape. Several circuit boards may be used to provide adequate area (sometimes referred to as board real estate) for the various electrical and electronic components required for the electronics and the electrical functions for the missile. Feed through connector devices are placed between otherwise adjacent circuit boards to connect electrically the respective circuits thereof to carry out intended functions. Missiles and like devices, such as torpedoes, rockets and other similar devices, undergo high stresses and accelerations during use, and it is difficult, but nevertheless important, to maintain the integrity of electrical connections in the electronics thereof for proper guidance, communications, munitions operations, etc. to avoid failures which may be not only expensive but also potentially catastrophic. Machines, portable electrical and electronic devices, for example, portable computers, and the like also need reliable electrical interconnects able to withstand normal and sometimes abusive conditions of mechanical forces.
A prior technique to interconnect circuits of stacked circuit boards in missiles, for example, has used a ball grid array of terminals on the respective circuit boards and an interface connector between the circuit boards. The interface connector includes an electrically nonconductive housing with through openings aligned generally with a respective ball contact on each of the adjacent circuit boards and with electrically conductive wool-like material, such as gold plated copper wool (of a form and texture similar to steel wool) in the openings providing a plurality of relatively light touch, small point connections with the ball terminals. Sometimes such conductive wool is referred to as fuzz buttons. There are a number of disadvantages to such a prior interconnect system. For example, the ball terminals must be soldered into respective concave terminal recesses in the circuit board; this is labor intensive (expensive), and it is possible for the solder connection to break under the stress of missile acceleration, thus causing a failure mode of the device. Breakage of a solder connection also is possible when the ball is not correctly aligned with the contact or pad to which it is intended for connection, thus resulting in a shear stress applied to the ball and or solder connection tending to break the connection. Another disadvantage is that acceleration may compress the wool-like material causing it to move away from the "up stream" ball terminal resulting in an open circuit failure. The manufacturing of the ball grid array of terminals of the circuit board, including the soldering of the balls in respective concave recesses without short circuits in a compact, relatively dense arrangement of such terminals, may be a difficult and time consuming task.
Thus, it will be appreciated that there is a need for a facile, robust and reliable interconnection mechanism for making feed through connections of circuits of stacked circuit boards or the like, especially for use in high stress environments, such as missiles, rockets and the like.
The need for electromagnetic interference (emi) shielding in many electronic devices is well known. Shielding between generally planar stacked devices and/or levels in a multilevel circuit board sometimes is provided by a conductive ground plane. Sometimes a case, e.g., an electrically conductive case, has been used to provide lateral shielding. Such shielding systems have been somewhat cumbersome, costly and space consuming. It would be desirable to facilitate such shielding and provision of ground connections in an electrical connector system and to provide easy selectability of such ground connections.